In general, processing in a process of manufacturing a semiconductor device or the like includes a liquid processing for removing particles or contaminants adhered to a substrate, for example, a semiconductor wafer (hereinafter referred to as “wafer”), by supplying the surface of the substrate with a process solution, such as a chemical solution or pure water.
As one of liquid processing apparatuses for performing such a liquid processing, there is a liquid processing apparatus that performs the liquid processing by placing substrates one by one on a spin chuck and supplying the surface of the substrate with a process solution while rotating the substrate. An example of this type of liquid processing apparatus includes a liquid processing apparatus having a plurality of liquid processing units capable of the same types of liquid processing, which improves the number of sheets of substrates processed per unit time (throughput of substrates) by carrying substrates to the plurality of liquid processing units by means of a common substrate carrying mechanism to thereby perform the liquid processing in parallel in the plurality of liquid processing units while continuously replacing the substrates. See Japanese Laid-Open Patent Publication No. 2008-034490 (e.g., paragraph 0020 and FIG. 1).
In such a liquid processing apparatus having a plurality of liquid processing units, a plurality of sheets of wafers contained in a substrate carrier, for example, an FOUP (Front-Opening Unified Pod), and carried into a factory are subjected to a predetermined sequence of liquid processing by taking out the wafers from the substrate carrier and introducing the taken wafers into the respective liquid processing units of the liquid processing apparatus in a predetermined sequence. Assuming that wafers contained in one FOUP corresponds to 1 lot, the liquid processing apparatus processes wafers in units of lots, based on a predetermined schedule, in normal operation conditions.
In some cases, however, there may be a need to urgently process unscheduled wafers contained in another FOUP, for example, at the request of a customer or for reasons of production controls, process tests, and the like. In a conventional solution, this urgent processing for the unscheduled wafers has been performed, for example, in such a manner as to wait until a liquid processing for a currently processed lot is ended and then start to preferentially process the lot of wafers to be urgently processed (hereinafter referred to as “priority lot”) before starting to process a next lot, or in such a manner as to completely stop the liquid processing for a currently processed lot and then start to process a priority lot.
According to this conventional solution, in the case of waiting until a liquid processing for a currently processed lot is ended, it is impossible to sufficiently meet the need for urgent processing because a point of time of starting to process a priority lot is delayed. Also, when a liquid processing for a currently processed lot is stopped for the moment and a priority lot intervenes, there occur unusual operations, such as an operation of stopping the currently processed lot or an operation of returning to the liquid processing after processing the priority lot, and thus there may be a fear of causing defects by failures in these unusual operations.
In Japanese Laid-Open Patent Publication No. Hei08-153765 (e.g., paragraphs 0146 to 0168 and FIGS. 20 to 28), a technique is disclosed which suppresses a lowering of throughput from being caused by a change in lots in a substrate processing apparatus for performing a series of processes for wafers, such as a process of coating or developing a resist film or the like, even when a priority lot having a different process flow intervenes. However, since this technique is also common to the above-mentioned liquid processing apparatus in that a processing for a currently processed lot must be stopped, it cannot solve the above problem with an operation of stopping or resuming the processing of a currently processed lot.